Large storage bins are used for various purposes including, for example, storage of building materials, starting materials for chemical processing operations, and, of course, materials associated with farming. The height, or axial length of large-volume storage bins can approach 40 meters. In order that such bins may be used as silos, or the like, they are provided at their lower end with an unloading or discharge hopper tapering downwards towards an outlet port such that even the slightest remainder of the bin contents will drop by gravity towards the outlet port. Because of the great weight of the materials stored in such large-volume bins, they must have high strength. In addition to a high load bearing strength for accommodating the load, it is also desirable that the bin, and its associated parts do not bulge or buckle under the pressure exerted by the stored materials. But in addition to these strength properties it is also important that the manufacturing costs be kept as low as possible. To this end, it is preferred to prefabricate the bins, and the essential parts thereof, to transport them to the site of use, and there to finally asssemble or mount them. It has already been known to provide substantially cylindrical main parts with a flange at the bottom front end. The front end of the unloading hopper having the largest outer diameter is matched to the inner diameter of the main part in the vicinity of the bottom front end thereof and is there welded to the main part. This weld is normally disposed at an axial spacing from the lower periphery or the bin flange. This, however, frequently gives rise to difficulties during welding because the weld is to be a continuous annular weld and it is not always possible to ensure uniform engagement of the outer periphery of the unloading hopper at the inner wall of the bin main part due to the frequently very large diameters in the order of e.g., a few meters. Thus very often non-uniform weldments are obtained, resulting in an unreliable joint between the main part and the hopper.
To avoid this disadvantage it has already been proposed to weld the upper front end of the unloading hopper directly to the bottom front end of the main part and to weld to this weld joint a further, approximately cylindrical member as a supplement, or auxiliary portion of the main part. However, in this case the distribution of forces is extremely unfavourable if no further measures such as the external fixing of a re-enforcing ring are taken.
Exemplary of prior storage containers or bins which have been proposed for holding a large volume of material are those disclosed in Italian Patent No. 555,940, Belgian Patent No. 553,154 U.S. Pat. No. 4,338,752 and U.S. Pat. No. 3,292,324. The containers disclosed in the patents have a number of shortcomings both from the standpoint of their relatively complex construction and/or their inherent weakness at critical load bearing areas. Thus, the container shown in Italian Patent No. 555,940 comprises a plurality of material holding sections, each of which differs in size from the other sections. An unloading hopper is secured by means of a thin, inwardly and downwardly angled flange to an L-shaped flange carried on the lowermost, and largest of the material holding sections. The bend in the flange in contact with the outer wall of the unloading hopper is positioned at a point of high stress and represents an area where metal fatigue can occur. The material holding sections, during transport, are positioned in nested relation to one another, and the unloading hopper is simply placed in the smallest of the sections with its upper, flange carrying end protruding from the inverted lower end of the smallest section.
The container of the Belgian Patent No. 553,154, like that of the Italian patent, comprises a plurality of material holding sections but differs from the container of the Italian patent in that the sections are of essentially the same size. The unloading hopper of the container shown in the Belgian patent is secured, as by welding, to the inner wall of a U-shaped ring member which, in turn, is secured by a bolt to an L-shaped flange secured on the outer wall of the lowermost material holding section. As in the case of the container of the Italian patent, the nexus of the unloading hopper and the lowermost section of the container is located at a high stress area, and is subject to metal fatigue. Transport of the container requires each section to be dismantled, and then reassembled at the point of use, a cumbersome, and time and space consuming operation.
U.S. Pat. No. 4,338,752 also discloses a container comprising a plurality material holding sections each of which differs in size from the other sections. The unloading hopper of the container has a relatively thin, annular, outwardly extending flange positioned around its upper edge. The flange is adapted to underlie a similar flange carried on the lower end of the largest and lowermost of the material holding sections of the container. Each flange is provided with a plurality of space holes which are in register with each other, and which receive bolts for attaching the hopper to the lowermost section. The material holding sections and the unloading hopper are placed in nested relation to one another during transport.
U.S. Pat. No. 3,292,324 also is concerned with a multiple component container which, due to its complexity, is cumbersome to handle and ship, and requires skilled personnel to erect. The unloading hopper of the container shown in the patent is supported on the bottom of the container by an inwardly facing, relatively, thin walled channel member, the free edges of which are welded to the wall of the hopper. The upper leg of the channel member is riveted to a leg of another, smaller, thin walled channel member bolted to the lowermost cell or material holding section of the container. Support for the hopper wall is limited to the line contact between the wall of the hopper and the lower leg of the inwardly facing channel member.